<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        *{
            margin: 0px;
            padding: 0px;
            /* 新的盒子模型 */
            box-sizing: border-box;
        }
        .box{
            height: 300px;
            padding: 0 300px;
        }
        .left, .center, .right{
            height: 300px;
            float: left;
        }
        .left, .right{
            width: 300px;
        }
        .center{
            width: 100%;
            background-color: gold;
        }
        .left{
            background-color: red;
            /* % 是相对于父的宽的% */
            margin-left: -100%;
            position: relative;
            left: -300px;
        }
        .right{
            background-color: blue;
            margin-left: -300px;
            position: relative;
            right: -300px
        }
    </style>
</head>
<body>
    <!-- 
        圣杯布局：三行三列    左右定宽   中间自适应
        特点：center写在前面
     -->
    <div class="box">
        <div class="center">中</div>
        <div class="left">左</div>
        <div class="right">右</div>
    </div>
</body>
</html>